Do Concrete Walls Need to Be Insulated?
Homes that have concrete walls in the basement or elsewhere still need insulation and weatherproofing for the owners to enjoy increased energy savings. Some contractors add foam insulation in the concrete form before pouring the cement while others add rigid board-type insulation on the exterior of the concrete after it hardens. However your basement walls are constructed, you'll likely want to insulate them.
Homes made with concrete block walls -- whether in the basement or not -- offer an opportunity to add insulation. Fill concrete block cores with insulation, except for the ones that require reinforcing rebar. The U.S. Department of Energy (DOE) recommends filling block interiors with high-pressure foam instead of vermiculite, perlite pellets or polystyrene beads.
Solid Concrete Walls
Insulate solid concrete walls by installing blocks of foam insulation inside the actual concrete form, which raises the R-value of the concrete and reduces the cold often found in concrete basements. Weatherproof the exterior of the concrete prior to backfilling or painting to add moisture and water protection to the home.
Autoclaved Concrete Block
Several concrete block manufacturers now include insulated materials in the concrete block construction. The DOE reported that two varieties, as of July 2011, were available for construction in the U.S. One is autoclaved cellular concrete and the other autoclaved aerated concrete. In the aerated version, the material consists of 80 percent air, by volume, and this type of autoclaved concrete lists 10 times the insulation value of uninsulated concrete.
Controversy surrounds the insulation of concrete basement walls, states the DOE. When insulating a concrete basement, the DOE indicates an annual energy savings of up to $450 a year using a two-inch foam insulation on the concrete basement wall. While not required, the DOE advises including insulation on the exterior wall of the conditioned basement space because the basement is attached to other areas of the house. With conduction and convection, uninsulated basement concrete walls can increase a home's annual energy usage.